This pressing instrument (1) to be used in bone surgery is equipped with a substantially columnar pressing member (3), one end of which has a pressing surface (3c) comprising a convex, substantially spherical surface, and further equipped with a hook member (2) which: is formed in a hook shape for engaging a lateral surface of a bone； has, on one end thereof, a support part (5) for supporting the pressing member (3) so as to have the pressing surface (3c) thereof facing the other end side； and has, on the other end thereof, a projecting part (6) that projects toward the support part (5) side thereof and bites into the lateral surface of the bone. Therein, the support part (5) supports in a manner such that the pressing member (3) is capable of moving in the lengthwise direction toward the projecting part (6) side.
